Nicaraguans cheered the Sandinistas as they marched triumphantly into Managua. Hundreds of thousands of citizens crammed in front of the National Palace to make the change of government official, welcoming Sandinista leaders and their victorious army.

Especially noticeable is a tremendous feeling of relief. "We're not afraid any longer," a bellboy says. "Now we can go out at night without wondering if we will return home," says a businessman.

Just as widespread is the deep sense of unity.

"We all think of the revolution as our child, and want to protect it, to give it a chance to grow. So we criticize everything, but not the revolution," explains Eduardo Kuhl, a coffee grower and hotel owner.

The Sandinistas inherited a bankrupct economy. General Somoza emptied the Treasury before he fled, leaving $3.5 million in the banking system and a whopping $1.6 billion foreign debt.

Areas that were destroyed must be rebuilt. Most factories were bombed.Communications and transport systems were in shambles. Thousands of houses and businesses were destroyed. Famine threatens because crops were not planted during the insurrection. Production ground to a halt during the war, so unemployment is widespread, hovering now around 30 percent.

Social needs are pressing, not just from the war, but from years of "Somocismo" in which there were great wealth for the few and grinding poverty for the many.

To make matters worse, the government faced incredibly high public expectations.

"Many Nicaraguans thought that once Somoza was gone, life would change instantly. But that just isn't possible," insists Dr. Moises Hassan Morales, one of the five members of the ruling junta.

The government passed over 200 decrees to get the country rolling and ease the burden of the poor, who are at least 75 percent of the population.

Rents under $150 a month were cut by almost half. The wages, about $1.80 a day, were raised slightly, and government salaries -- even those of the junta -- were limited to $1,000 a month. Prices of basic foods like rice, beans, and milk are controlled to keep the lid on inflation.

Schools and medical care, which were previously unavailable to most Nicaraguans (because fees were charged), were made free. Unions, which were either powerless or crushed, now are organizing furiously and have real strength. A hundred thousand workers already have formed unions, under the approving eyes of the Sandinistas, and 60,000 peasants have joined the farm workers' union.

Elections are occurring in the "mass" organizations (the block committees, women's and youth groups, and unions) and in local governments. Many Nicaraguans are participating in decisionmaking for the first time.

Economic plans for 1980 are ambitious. The government will try to create 90, 000 jobs, though many observers doubt this is possible so soon.

Bombed-out buildings are being rebuilt, and roads, parks, hospitals, and the like are being constructed in every part of the country. Most of the housing that had been destroyed in Managua, in fact, is already completed.

Perhaps most important, a mass campaign to teach basic reading and writing to the 53 percent of Nicaraguans who are illiterate will begin in March.

All these improvements must be paid for out of production, which creates something of a dilemma for the new leaders, who have promised much.

"We can't afford to consume our resources now. We must work and reinvest them," says Henry Ruiz, the nation's new planning minister.

The country is potentially rich, and could indeed provide the social goods -- for example, education, health care, housing, and some of the jobs -- that leaders now promise if it can just get out of the current impasse, produce enough to earn foreign exchange, repay the debt, and accumulate surplus.

What is interesting is that despite the staggering problems, the government and Sandinista leaders command the loyalty of most of Nicaragua's 2.5 million people.

"The people trust the new government. After all, they were part of the insurrection together," observes Mary Hartman, an American nun who has here for 15 years.

"They aren't afraid of austerity either, because most Nicaraguans always lived [with] it, along with repression. Now it's just austerity. And they are confident things will change."

Not all, of course, are satisfied.

Not unexpectedly, the sharpest complaints are from those with large business or land holdings, who fear the government is too committed to the poor and not concerned enough with the needs of the private sector. A key business organization, the Superior Council of the Private Sector, has endorsed the government's economic plan for this year, but is clearly edgy about what latitude the Sandinistas will allow for it and how the government expects it to help out.

The influential daily newspaper La Prensa, as wella s news organizations representing the political left and right, have also criticized the six-month-old government. In part, this indicates a positive shift -- the government feels comfortable enough to relax some of the controls it instituted after taking power.

The private sector's dissatisfaction is noteworthy, because, controlling 60 percent of the economy, its cooperation is essential if the ailing economy is to revive. The government also needs the private sector's investment and managerial know-how.

Businessmen are skeptical, however, of the Sandinistas's growing political power. They fear that someday their holdings may be nationalized.

They point out the government already has put strong controls on finance and foreign trade. It extends credit for business ventures it feels are most needed -- for example, to produce necessities like food, clothing, and medicine, and to market key export products like cotton and coffee. And it regulates what is imported and exported.

It woos private enterprise with easy loans, good prices, and quick payment for products the governmental then markets; thus eliminating the middlemen.

The Sandinistas promise a certain degree of labor peace, too. They are launching a campaign to hold down wage demands and increase labor productivity.

But the government has hinted it can use its muscle againt business. If the large landholders, for example, leave fertile land uncultivated, it will lease the lands for nominal fees to others who are more willing to cultivate it.

Jaime Balcazar, head of a UN mission here, says the Nicaragua government is "not communist, as some in the US say, or capitalist with new face, as some of the ultra-left critics here claim. Nor is it anything in between. Rather, the mide is purely Sandinista."